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Revert "mm: use early_pfn_to_nid in page_ext_init"

[ Upstream commit 2f1ee09 ]

This reverts commit fe53ca5 ("mm: use early_pfn_to_nid in
page_ext_init").

When booting a system with "page_owner=on",

start_kernel
  page_ext_init
    invoke_init_callbacks
      init_section_page_ext
        init_page_owner
          init_early_allocated_pages
            init_zones_in_node
              init_pages_in_zone
                lookup_page_ext
                  page_to_nid

The issue here is that page_to_nid() will not work since some page flags
have no node information until later in page_alloc_init_late() due to
DEFERRED_STRUCT_PAGE_INIT.  Hence, it could trigger an out-of-bounds
access with an invalid nid.

  UBSAN: Undefined behaviour in ./include/linux/mm.h:1104:50
  index 7 is out of range for type 'zone [5]'

Also, kernel will panic since flags were poisoned earlier with,

CONFIG_DEBUG_VM_PGFLAGS=y
CONFIG_NODE_NOT_IN_PAGE_FLAGS=n

start_kernel
  setup_arch
    pagetable_init
      paging_init
        sparse_init
          sparse_init_nid
            memblock_alloc_try_nid_raw

It did not handle it well in init_pages_in_zone() which ends up calling
page_to_nid().

  page:ffffea0004200000 is uninitialized and poisoned
  raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
  raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
  page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
  page_owner info is not active (free page?)
  kernel BUG at include/linux/mm.h:990!
  RIP: 0010:init_page_owner+0x486/0x520

This means that assumptions behind commit fe53ca5 ("mm: use
early_pfn_to_nid in page_ext_init") are incomplete.  Therefore, revert
the commit for now.  A proper way to move the page_owner initialization
to sooner is to hook into memmap initialization.

Link: http://lkml.kernel.org/r/20190115202812.75820-1-cai@lca.pw
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
  • Loading branch information...
cailca authored and gregkh committed Feb 12, 2019
1 parent 538162d commit 5a8da52a2982c3d5edfe17b9a56971b7dc3eaa38
Showing with 3 additions and 4 deletions.
  1. +2 −1 init/main.c
  2. +1 −3 mm/page_ext.c
@@ -663,7 +663,6 @@ asmlinkage __visible void __init start_kernel(void)
initrd_start = 0;
}
#endif
page_ext_init();
kmemleak_init();
debug_objects_mem_init();
setup_per_cpu_pageset();
@@ -1069,6 +1068,8 @@ static noinline void __init kernel_init_freeable(void)
sched_init_smp();

page_alloc_init_late();
/* Initialize page ext after all struct pages are initialized. */
page_ext_init();

do_basic_setup();

@@ -396,10 +396,8 @@ void __init page_ext_init(void)
* We know some arch can have a nodes layout such as
* -------------pfn-------------->
* N0 | N1 | N2 | N0 | N1 | N2|....
*
* Take into account DEFERRED_STRUCT_PAGE_INIT.
*/
if (early_pfn_to_nid(pfn) != nid)
if (pfn_to_nid(pfn) != nid)
continue;
if (init_section_page_ext(pfn, nid))
goto oom;

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